Liquid fuel burner

ABSTRACT

A liquid fuel burner so constructed that a Silocco fan is disposed in a gasification chamber of the burner and an atomizer utilizing the effect of centrifugal force is provided in the center or air-sucking portion of said Silocco fan, whereby a liquid fuel supplied to the atomizer is dispersed radially outwardly under the influence of centrifugal force in the form of particles and further divided into fine particles by the stirring and dispersing actions of the blades of said Silocco fan, said fine particles of liquid fuel being gasified by heated air.

I United States Patent 1151 3,640,673

Okamoto et al. 451 F b, 8, 1972 [S4] LIQUID FUEL BURNER [56] ReferencesCited [72] Inventors: Kenya Okamoto; Hailme Satoda, both of UNITEDSTATES PATENTS Nara- Japan 1,971,874 8/1934 Perry ..431/168 X 731Assignee: Matsushita Electric Industrial 00., 1.111., 2905352 6/1935Branche- 431/168 Osaka, Japan 2,718,919 9/1955 Ray ..431/1e3 x [22] Fied: July 20,19 0 3,021,892 2/1962 Brula ..431/168 [21] Appl. No.: 56,257Primary Examiner-Edward G. Favors Attorney-Stevens, Davis, Miller &Mosher 30 Fore A [1 ti Pri t D ta 1 1 a pp y a [57] ABSTRCT July 22,1969 Japan ..44/5958l July 22,1969 Japan ..44/59582 A hquld fucl burnerconstructed that a Silocco fan 15 a July 22,1969 Japan" 44/7165;disposed in a gasification chamber of the burner and an July 22, 1969Japan ..44/71659 atomizer utilizing the elfect of centrifugal force isProvided in the center or air-sucking portion of said Silocco fan,whereby [52] US. CL... ...431/ 168, 239/2l4.15, 431/208 a liquid fuelsupplied to the atomizer is dispersed radially out- [51] Int. Cl ..F23d11/04 wardly under the influence of centrifugal force in the form of 1Field of Search 207, 11, particles and further divided into fineparticles by the stirring and dispersing actions of the blades of saidSilocco fan, said fine particles of liquid fuel being gasified by heatedair.

9 Claims, 7 Drawing Figures PAIENIEnrm a ma SHEET 3 OF 3 FIG.7

LIQUID FUEL BURNER The present invention relates to a liquid fuel burnerwhich is so designed that a liquid fuel is burned after it has beencompletely gasified, whereby the combustion efficiency is enhanced andthe combustion noise is minimized.

Various types of liquid fuel burners have been proposed heretofore, ofwhich one is a pot type and the other is a gun type or rotary typewherein fuel is atomized. In the pot type, a fuel stored in the bottomof a combustion cylinder is gasified by the combustion heat and burntsuccessively. However, since the fuel is gasified only naturally, thecombustion capacity is inevitably subjected to a limitation and inaddition, the quantity of soot formed becomes large and the funnelconstruction becomes complicated.

In the type wherein fuel is atomized, the particles of fuel are mixedwith air for the first time when they reach a combustion region, so thata red flame tends to occur during combustion and a large quantity ofsoot is formed.

The red flame combustion may be converted into an efficient blue flamecombustion by supplying excess air. However, a type of burner whereinair is supplied in an excessive quantity to obtain a blue flamecombustion, has the disadvantages that the combustion is accompanied bya large noise and that carbon monoxide is generated due to incompletecombustion, such as lifting.

The present invention aims to eliminate such disadvantages of theconventional burners, by gasifying fuel completely and mixing thegasified fuel with air thoroughly before the fuel reaches a combustionregion.

An object of the invention is to provide a liquid fuel burner wherein aSilocco fan is disposed in a gasification chamber of a burner elementand an atomizer utilizing the effect of centrifugal force is provided inthe center or air sucking portion of said Silocco fan to disperse theliquid fuel supplied thereto radially outwardly under the influence ofcentrifugal force in the form of particles, said particles of fuel beingfurther divided into fine particles by the stirring and dispersingactions of the blades of said Silocco fan and gasified by preheated air,whereby the fuel is gasified and burnt efficiently in the form of a blueflame and moreover the combustion noise is minimized.

Another object of the invention is to provide a liquid fuel burner ofthe character specified above, wherein the Silocco fan is rotated at arelatively low rate at the initiation of combustion so as to avoidsupply of a excessively large quantity of air relative to the quantityof fuel supplied, whereby flame lifting can be prevented and thecombustion range at the initial stage of combustion is expanded.

Still another object of the invention is to provide a liquid fuel burnerof the character specified above, wherein an air suction passage for theSilocco fan is formed adjacent the combustion region, so that in thenormal combustion operation the air being sucked may be preheated by thecombustion heat, without using a heater, etc., to further promote thegasification of fuel.

Still another object of the invention is to provide a liquid fuel burnerof the character described above, wherein the air inlet portion of saidair suction passage is shielded from the combustion region, wherebymixing of the combustion gases in the air being sucked is prevented andhence the combustion efliciency is enhanced.

Still another object of the invention is to provide a liquid fuel burnerof the character described above, wherein the fuel is supplied to theatomizer from above the center of said Silocco fan, whereby piping of afuel supply pipe is simplified.

Still another object of the invention is to provide a liquid fuel burnerof the character described above, wherein flame holes communicating withthe gasification chamber are formed between a mixing rang and acombustion ring and between the combustion ring and a headplate, and theinner edge of the mixing ring is projected into the gasificationchamber, whereby mixing of the gasified fuel and air is further promotedand the formation of a red flame or generation of soot due toinsufficient mixing can be prevented.

A further object of the invention is to provide a liquid fuel burner ofthe character described above, which further comprises a fuel supplydevice comprising a main tank provided with a level-adjusting mechanismto control the level of fuel therein and having an inlet for fuel from afuel tank, an auxiliary tank smaller in capacity than said main tankcommunicating with said main tank at a lever above a set level of fuelin the main tank and having an outlet for fuel at a level lower thansaid communicating level, and a pump for pumping the fuel from said maintank into said auxiliary tank, the pump having a pumping capacitygreater than the flow rate of fuel discharged through said outlet,whereby the fuel is supplied to the burner element always at a constantrate even if the pumping capacity of the pump varies, and hence auniform combustion is obtained at all times.

Other objects, features, and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. I is a sectional view of an embodiment of the liquid fuel burneraccording to the present invention;

FIG. 2 is a front elevational view of the burner element, with halfportion shown in section;

FIG. 3 is an enlarged sectional view of the fuel atomizing portion;

FIG. 4 is a diagram of a combustion control circuit;

FIGS. 5 and 6 are enlarged sectional views of other arrangements of thefuel atomizing portion; and

FIG. 7 is a sectional view of the fuel supply device.

One embodiment of the liquid fuel burner according to the presentinvention will be described hereunder with reference to FIGS. 1-4.

Referring to FIGS. 1-3, reference numeral 1 designates a mounting frameand 2 designates a burner element mounted on top of said mounting frame.A space 1 is formed between the mounting frame 1 and the burner element2 by spacers 3 interposed therebetween.

Reference numeral 4 designates a casing of the burner element 2, whichconsists of an inner casing 5 and an outer casing 6. The inner casing 5and the outer casing 6 define therebetween a space which is used as anairflow passage 7, and an annular projection 8 is formed extendingoutwardly from the upper portions of said casings. Reference numeral 9designates a number of air inlet holes bored through the peripheral wallof the annular projection 8, and 10 designates the peripheral edges ofthe inner and outer casings S, 6 which are flexed downwardly so as tocover the air inlet holes 9 from above and outside thereof. Referencenumeral 11 designates a heater wound around the outer surface of theinner casing 5,

. and 12 designates a mixing ring fixed to the edge of the opening ofthe inner casing 5. A combustion ring 14 is provided above the mixingring 12 with spacers 13a interposed therebetween, and further aheadplate 15 is provided above the combustion ring 14 with spacers 13binterspaced therebetween, said spaces 13a, 1312 being respectivelyspaced from each other so as to define slitlike flame holes 16. Thespace 17 defined by the inner casing S and the headplate 15 is used as agasification chamber and the inner peripheral edge of the mixing ring 12is projecting into said gasification chamber 17.

Reference numeral 18 designates an air passage hole formed centrally ofthe bottom wall of the inner casing 5, and 19 designates a heatinsulating material, such as asbestos, surrounding the outer peripheralsurface of the outer casing 6 and being held in position by a cover 20.Reference numeral 21 designates a motor secured to the underside of themounting frame 1 by means of a bracket 22, with the drive shaft 23thereof extending upwardly through the bottom walls of the cover 20 andthe outer casing 6 and further through the air passage hole 18 in theinner casing 5, into the gasification chamber 17. In the gasificationchamber 17 is provided a Silocco fan 24. Reference numeral 25 designatesan atomizer plate mounted on the drive shaft 23 of the motor 21 in thecentral portion of the Silocco fan 24, and 26 designates a fuel supplypipe having one end located above the atomizer plate 25 in opposedrelation thereto, with the other end connected to a solenoid valve 27.Reference numeral 28 designates a pipe connecting the solenoid valve 27with a liquid fuel supply device 29; 30 a cooling fan for the motor 21;and 31 a cooling air inlet hole formed in the mounting frame 1.Reference numeral 32 designates an ignition plug; 33 a heat-sensingelement which controls a current conducted through the heater 11 uponsensing the temperature of the casing 4, particularly of the innercasing 5; and 34 a combustion sensing element which senses thecombustion state of the burner element 2. The electrical connection andthe functions of these elements will be described in detail later.

The liquid fuel burner constructed as described above operates in thefollowing manner: Namely, when the motor 21 is set in motion to rotatethe Silocco fan 24 and the atomizer plate 25, and heater 11 is energizedand the solenoid valve 27 is opened, air flows into the airflow passage7 from the outside through the air inlet holes 9 of the casing 4, underthe suction produced by the Silocco fan 24. In this case, the innercasing 5 is heated by the heater 11, so that the air is heated by theinner casing 5 and the heater 11 during passage through the airflowpassage 7, and flows into the central portion of the Silocco fan 24through the air passage hole 18 of the inner casing 5 in the heatedcondition. Thereafter, the air is dispersed within the gasificationchamber 17.

On the other hand, a metered quantity of fuel supplied from the fuelsupply device 29 passes through the solenoid valve 27 and the fuelsupply pipe 26 and is fed onto the rotating atomizer plate 25.

The fuel on the atomizer plate 25 is splashed outwardly as shown in FIG.3 by the centrifugal force imparted thereto, further accelerated andstirred by the blades of the Silocco fan 24 and finally atomized in theform of fine particles.

Since the Silocco fan 24 is also dispersing the heated air, the fineparticles of fuel which are small in heat capacity, are gasified almostentirely as soon as they contact the heated air, and the remaining fuelparticles are gasified by contact with the inside surface of the innercasing 5 which is heated by the heater 11.

The gasified fuel and the heated air are thoroughly stirred and mixedwithin the gasification chamber 17, since the inner edge of the mixingring 12 projects inwardly of said gasification chamber, and thereafterejected to the outside through the slit-shaped flame holes 16 defined bythe combustion ring 14 and the heat plate 15, etc. By igniting theair-fuel mixture by means of the ignition plug 32, an annular flame A isformed.

The flame A is formed adjacent the annular projection 8 of the casing 4,so that the air flowing into the gasification chamber 17 through the airinlet holes 9 is heated by the flame to a higher temperature thanbefore, without being heated by the heater 11.

The air thus heated gasifies completely the fuel, dispersed by theatomizer plate 25 radially and atomized into fine particles, before theparticles reach the inside surface of the inner casing 5. Thus, it willbe understood that the current supply to the heater 11 is necessary onlyat the start of combustion, and not necessary thereafter.

As stated, the combustion flame A is formed adjacent the projection 8 ofthe casing 4 and the peripheral wall of the projection 8 has the airinlet holes 9 bored therethrough, so that the combustion gases would bemixed in the air flowing into the gasification chamber, unless somemeans is provided. The mixing of the combustion gases into the air meansthat the quantity of oxygen per unit volume of air is decreased and asteady combustion cannot be expected due to the development of sootduring combustion and in complete combustion. In the burner of thisinvention, since the peripheral edge of the casing 4 is flexed so as tocover the inlet holes 9 from above and the front side. Therefore, thecombustion gases are not allowed to reach the air inlet holes 9 and theair is admitted only from the lower side of the holes.

As a result, no combustion gases are mixed in the air and a steadycombustion can be obtained.

The motor 21 is protected from the combustion heat by theheat-insulating material 19 provided along the outer peripheral surfaceof the outer casing 6, and is cooled by the cooling fan 30. A layer ofair flowing in the gap t between the casing 4 and the mounting frame 1also serves to insulate the motor 21 against the combustion heat.

At the initiation of combustion, the heater 11 heats the inner casing 5and also the air passing through the airflow passage 7, as stated above,At this point, however, since the burner element 2 has not beensufficiently heated, the temperature of the air flowing into the burnerelement and the temperature of the inner casing 5 are not so high.Consequently, the fuel dispersed by the atomizer plate 25 and stirred bythe blades of the Silocco fan into fine particles is not entirelygasified initially, and a part thereof remains in the bottom of theinner casing 5 in the form of liquid.

The fuel is completely gasified when the burner element 2 has beensufficiently heated by the combustion heat.

In the burner of this invention, the rate of rotation of the motor 21 islowered only for a period in which the gasification of fuel isinsufficient, so as to decrease the quantity of air blown by the Siloccofan 24. This is because, if the quantity of air blown by the fan islarge relative to the quantity of fuel being gasified, lifting tends tooccur during combustion resulting in flame out or generation of carbonmonoxide clue to incomplete combustion.

Referring to FIG. 4, there is shown an electric circuit for controllingthe rate of rotation of the motor 21 and the combustion of fuel.

In FIG. 4, reference numeral 35 designates a primary circuit having avoltage of V. impressed across the terminals 36, 37 thereof, and 38designates a secondary circuit arranged with a transformer 39 interposedbetween it and said primary circuit 35 and impressed with a voltage ofabout 24 V.

The primary circuit 35 includes the circuit 40 of the heater 11, thecircuit 41 of the motor 21, the circuit 42 of the ignition plug 32 andthe circuit 43 of the solenoid valve 27. The motor circuit 41 isdiverged into a low-speed circuit 41a and a high- Speed circuit 41b.

Reference numeral 44a designates a relay switch inserted in the heatercircuit 40; 45b a relay switch inserted in the motor 41; 45b a relayswitch inserted in the solenoid valve circuit 43; 46a a bimetal switchto switch the motor circuit 41 from the low-speed circuit 41a to thehigh-speed circuit 41b or vice versa; and 46b a bimetal switch connectedto the motor circuit 41 and operated for engagement with a contact 47 or48 of the ignition plug circuit 42. In the secondary circuit 38,reference numeral 49 designates a bimetal switch to ensure safety of thecircuit, and the current flowing throughout the circuit 38 isinterrupted when said safety switch is opened. Reference nu meral 44bdesignates a relay switch which switches the electrical connection froma contact 50 or 51 or vice versa; 450 a relay switch; 52 a switch whichis opened and closed by the function of the heat sensing element 33; 53a switch which is opened and closed by the function of thecombustion-sensing element 34; 54, 55 relay coils; and 56, 57 heatersfor the bimetal switches. The relay switches 44a, 44b are operated bythe relay coil 54, such that when a current flows through the relay coil54, the relay switch 44a is closed and the relay switch 44b is broughtinto contact with the contact 51.

The relay switches 54a, 45b, 45c are operated by the other relay coil55, such that when a current flows through the relay coil 55, all of therelay switches 45a, 45b, 450 are closed.

The safety bimetal switch 49 is designed to be opened a while after theheater 57 is energized. When the other heater 56 is energized, thebimetal switch 46a is connected to the high-speed circuit 41b and thebimetal switch 46b to the contact 48.

For initiating the combustion operation, with the arrangement describedabove, a voltage is first of all impressed across the terminals 36, 37.In the secondary circuit 38, the current flows through the relay coil 54only, whereby the relay switch 44a of the heater circuit 40 is closedand the other relay switch 44b is contacted with the contact 51. Then,the inner casing 5 is heated to a predetermined temperature by theheater ll, whereupon the temperature of said inner casing 5 is sensed bythe heat-sensing element 33 and the switch S2 is closed. Here, thecurrent also passes through the other relay coil 55, so that the relayswitches 45a, 45b, 450 are all closed and the current flows through thelow-speed circuit 41a of the motor 21, the solenoid valve circuit 43 andthe ignition plug 32. As a result, the burner element 2 starts itsoperation, with the motor 21 rotating at a low speed. When the flame Ais formed in the burner element 2, such state is sensed by thecombustionsensing element 34 and the switch 53 is opened. Since thecurrent no longer passes through the relay coil 54, the relay switch 44ais opened to interrupt the current supply to the heater 11. The otherrelay switch 44b is switched to the contact 50 to deenergize the heater57 and energize the heater 56. Upon energization of the heater 56, thebimetal switch 460 is switched to the high-speed circuit 41b and theother bimetal switch 46b to the contact 48. Thus, the motor 21 rotatesat a high speed and the burner element 2 is brought into the state ofnormal operation. The current supply to the ignition plug 32 is alsointerrupted. The heat-sensing element 33 is heated by the combustionheat during normal operation of the burner element, and hence the switch52 is held closed.

If, in the initiation of the combustion operation described above, thecombustion flame A is not formed in spite of the fact that allconditions for starting the combustion are satisfied, thecombustion-sensing element 34 does not open the switch 53 and thecurrent continues to flow through the relay coil 54. In this case, therelay switch 44b is of course still in engagement with the contact 51and the heat 57 continues to generate heat, so that the safety bimetalswitch 49 is opened. Consequently, no current flows through thesecondary circuit 38 and the combustion starting operation is onceinterrupted. The safety bimetal switch 49 is opened on occurrence of anabnormal condition, such as ignition failure or fuel supply failure. Insuch a case, the mechanism should be inspected to ensure that thecomponent parts are in a satisfactory condition, because otherwise thecondition will possibly lead to malfunction of the mechanism.

In the liquid fuel burner of the invention, as described above, theliquid fuel gasification unit, comprising the Silocco fan and the fuelatomizer plate disposed in the control portion of said Silocco fan, isprovided in the casing which has the air flow passage therein adjacentthe flame holes, and the motor for driving said Silocco fan is rotatedat a relatively low speed at the start of combustion. Therefore, liquidfuel is atomized into fine particles by the centrifugal force of theatomizer plate and the stirring action of the blades of the Silocco fan,and is readily gasified by heating it slightly at the initiation of thecombustion operation. The fuel is gasifled and burned from the outset ofthe combustion operation and thereafter the gasifrcation of fuel iseffected by the heated air.

Since the gasifred fuel and air are completely mixed prior tocombustion, an excellent blue flame combustion, free of soot, can beobtained. Furthermore, the combustion is not accompanied by a noisesince supply of excess air is unnecessary.

At the initiation of combustion, the casing of the burner element is notheated and hence the rate of gasification of fuel is low. In the burnerof this invention, the quantity of air blown by the Silocco fan isdecreased at this point, by reducing the rate of rotation of the motor.Therefore, occurrence of lifting due to excess air can be avoided and asteady combustion can be obtained from the outset of the combustion. Inother words, the range of combustion can be expanded by changing therate of rotation of the motor.

The table provided below shows the combustion range in the case (B)wherein the quantity of air blown by the Silocco fan is maintainedconstant without changing the rate of rotation of the motor, and thesame in the case (C) wherein the quantity of air blown by the Siloccofan is changed by reducing the rate of rotation of the motor to, e.g.,30 percent of the normal rate of rotation. In this table, the roomtemperature is -l 0 C. and the flow rate of air blown by the Silocco fanunder normal condition is 46.5 mP/hr.

Control of Combustion Rate Motor Rotation (Fuel Quantity) No (B) 3.2-4.2Llhr. Yes (C) 2.7-4.2 Llhr.

In the above table, the minimum value of the combustion rate is thelimit beyond which lifting occurs, and the maximum value of the same isthe limit beyond which a red flame occurs.

From the results shown in the table, it will be seen that the combustionrange can be expanded 50 percent by reducing the flow rate of air blownby the Silocco fan by 30 percent, by reducing the rate of rotation ofthe motor, and that thereby a safe combustion free of lifting can beobtained at the initiation of combustion, even if the rate ofgasification of fuel is low. Namely, the starting characteristic ofcombustion can be markedly improved.

The other arrangements of the fuel atomizing portion will be describedhereunder with reference to FIGS. 5 and 6.

In the arrangement shown in FIG. 5, an atomizing cap 59 having a largenumber of atomizing holes 58 perforated through the peripheral wallthereof, is provided by forming a depression at the center of the upperplate of the Silocco fan 24, and the discharge end of the fuel supplypipe 26 is located above said atomizing cap 59 in opposed relationthereto.

The atomizing effect of this arrangement is the same as that in thepreceding embodiment. Namely, the fuel fed into the atomizing cap 59from the discharge end of the fuel supply pipe 26 is ejected in the formof fine particles through the holes 58 under the influence ofcentrifugal force and further divided by the stirring and dispersingaction of the blades of the Silocco fan 24.

In this arrangement, the atomizing cap 59 is formed on the upper plateof the Silocco fan 24, for the following reason:

Namely, the atomizing cap 59 has the effect of radially dispersing theliquid fuel fed therein, under the influence of centrifugal force anddividing the fuel into coarse particles before it is stirred by theblades of the Silocco fan 24.

In this view, it would be satisfactory to connect an atomizer plate tothe shaft 20 of the motor 18 in the central portion of the Silocco fan24, as shown in the arrangement of FIGS. 1-3. However, according to sucharrangement, the fuel supply pipe is inevitably extended into thecentral space of the Silocco fan 24. Consequently, the piping of thefuel supply pipe becomes difficult and the pipe may interfere with therotation of the Silocco fan 24, and further the diameter of the pipeundergoes a limitation since the pipe is extended into the central spaceof the fan.

In the arrangement shown in FIG. 5, however, since the atomizing cap 59is open in the upper plate of the Silocco fan 24, ti is unnecessary toextend the fuel supply pipe 26 into the central portion of the Siloccofan 24 and the pipe can be arranged within the gasification chamber 17.Therefore, the piping of the fuel supply pipe 26 is easy and therotation of the Silocco fan is not interfered by the pipe at all. Inaddition, the diameter of the pipe can be made large and clogging of thepipe with dusts, etc., can be avoided.

Fig. 6 shows another arrangement in which the atomizing cap 59 isprovided separately from the upper plate of the Silocco fan 24. Theeffect of this arrangement is identical with that of the arrangement ofFIG. 5. In FIGS. 5 and 6, reference numerals 60, 61 designate aplurality of fuel receiving plates provided on that portion of the fuelsupply pipe 26 which extends in the interior of the gasification chamber17, the diameter of said plates being reduced upwardly. These receivingplates 60, 61 serve to receive the fuel flowing down onthe outerperipheral surface of the fuel supply pipe 26 and quickly gasifies thesame. Namely, a part of the fine fuel particles dispersed by the Siloccofan 24 collides against the fuel supply pipe 26 and flows down in theform of liquid along the outer peripheral surface of said pipe to beaccumulated in the plates 60, 61. The air present in the gasificationchamber wherein the receiving plates 60, 61 are located, is previouslyheated and maintained at a predetermined elevated temperature by thecombustion heat. Therefore, the fuel received by the receiving plates60, 61 is gasified is sequence to be served for combustion.

The fuel attached to the wall of the fuel supply pipe 26 is gasified inthe process of flowing down on the wall and a very little amount of fuelreaches the receiving plates 60, 61. In the initiation of combustion,however, the fuel is hardly gasified on the wall of the fuel supply pipe26, so that the plurality of receiving plates 60, 61 are provided forthe sake of safety and such that the fuel overflowing the upper plate 60may be received by the lower plate 61, if such overflow occurs.

As may be understood from the foregoing description, the provision ofthe fuel receiving plates to receive the fuel flowing down along theouter peripheral surface of the fuel supply pipe 26 and to gasify thesame, is advantageous, not only in that the fuel dispersed by theSilocco fan 24 can be entirely served for combustion, but also that theaccumulation of tar on the surface of the burner casing, particularly onthe bottom surface of the inner casing, can be avoided.

Now, the construction of the fuel supply device 29 will be describedwith reference to FIG. 7. In FIG. 7, reference numeral 62 designates amain tank having a fuel inlet passage 63 formed in the bottom thereof,said fuel inlet passage 63 being communicated with a liquid fuel tank(not shown), and 64 designates a guide cylinder formed integrally withthe wall of said fuel inlet passage 63 and having a valve seat 65 formedin the bottom wall thereof at a location where the inside cavity of saidguide cylinder communicates with the fuel inlet passage 63. Referencenumeral 66 designates a filter removably disposed in the inlet passage63; 67 a fuel passage hole formed through the peripheral wall of saidg$ide cylinder 64; and 68 a valve body vertically slidably fitted insaid guide cylinder 64 to open and close the valve seat 65, said valvebody being normally urged upwardly by a spring 69 to keep the valve seat65 open. Reference numeral 70 designates a lever pivotally connected toa projection 71 by a pin 72, which projection 71 extends upright fromthe flange formed around the open top edge of the guide cylinder 64. Oneend of the lever 70 is in abutting engagement with the top end of thevalve body 68 and the other end thereof is provided with a float 73.

The float 73 maintains the surface of the fuel in the main tank 62 at apredetermined level in cooperation with the lever 70 and the valve body68. Namely, when the surface of fuel lowers, the float 73 movesdownward, causing the lever 70 to rotate in a clockwise direction,whereby the value body 68 opens the valve seat 65. Thus, it will be seenthat the fuel is supplied into the main tank 62 through the fuel inletpassage 63, the filter 66, the valve seat 65 and the fuel passage hole67, until the surface thereof reaches the predetermined level. Referencenumeral 74 designates an auxiliary tank formed at the upper portion ofone sidewall of the main tank 62. This auxiliary tank 74 is communicatedwith the upper portion of the main tank 62 through a communication port75 and is provided with a fuel outlet port 77 on one sidewall thereof,said fuel outlet port 77 having an orifice 76 therein. The capacity ofthe auxiliary tank 74 is very small as compared with the capacity of themain tank 62. The communication port 75 is positioned at a lever higherthan the set level of fuel and the fuel outlet port 77. Referencenumeral 78 designates a pump by which the fuel in the main tank 62 issent into the auxiliary tank 74. The pumping capacity of the pump 78 isset to be greater than the quantity of fuel discharged through theorifice 76 at a predetermined rate. Reference numeral 79 designates acover. The fuel outlet port 77 is connected to the connecting pipe 28shown in FIG. 1.

With the construction described above, when the pump 78 is actuated andthe aforesaid solenoid valve 27 is opened, the fuel introduced into theauxiliary tank 74 from the main tank 62 is supplied to the burnerelement 2 at a predetermined rate established by the orifice 76. Sincethe pumping capacity of the pump 78 is greater than the quantity of fuelsupplied through the orifice 76, the fuel level in the auxiliary tank 74rises gradually and reaches the level of the communication port 75 butwill not rise higher than the communication port because excess fuel isreturned into the main tank 62 through said communication port.

Thus, a predetermined quantity of fuel is maintained in the auxiliarytank 74. Therefore, the fuel is supplied to the burner element always ata constant rate through the orifice 76. even when the fuel supply rateof the pump 78 varies due, for example, to a voltage fluctuation orfrequency fluctuation.

If the solenoid valve 27 is not closed due to malfunction when thecurrent supply to said solenoid valve and the pump 78 is interrupted,the fuel remaining in the auxiliary tank 74 will flow into the burnerelement but the quantity thereof is so small that it will not cause anyproblem.

The conventional liquid fuel burner is unsatisfactory in this point andhas the drawback that, once the solenoid valve has failed and is heldopen, the entire fuel in the fuel tank flows into the burner through themain tank, because in the burner an auxiliary tank is not provided andthe main tank is directly connected to the solenoid valve.

According to the present invention, however, the auxiliary tankextremely smaller in capacity than the main tank is provided to storethe fuel before the fuel is fed to the burner. Therefore, only a smallquantity of fuel flows into the burner even if the solenoid valve is notclosed, and the degree of danger can be lessened accordingly.

In addition, the fuel is fed to the burner always at a constant rateeven if the pumping capacity of the pump varies, whereby uniformcombustion can be obtained.

As may be understood from the foregoing description, according to thepresent invention there is provided a liquid fuel burner which iscapable of burning a liquid fuel efficiently and uniformly, with aminimum noise. The burner of the instant invention can be used in a verywide range of application, e.g., as a stove, a hot water boiler, etc.

Although the present invention has been described and illustrated hereinin terms of a specific embodiment thereof, it is to be understood thatmany changes and modifications are possible without deviating from thespirit of the invention.

What we claim is:

1. A liquid fuel burner comprising a burner casing consisting of aninner casing defining therein a gasification chamber communicating withflame holes and an outer casing surrounding said inner casing anddefining an airflow passage between it and said inner casing, a Siloccofan disposed in the central portion of said gasification chamber to suckthe air in said airflow passage at the center thereof and disperse thesame radially outwardly, a fuel atomizer provided in the central portionof said Silocco fan for rotation therewith and adapted to atomize theliquid fuel under the influence of centrifugal force, means forpreheating the air passing through said air flow passage and saidgasification chamber, and means for supplying the fuel to said atomizer.

2. A liquid fuel burner as defined in claim 1, wherein means is providedto rotate said Silocco fan at the initiation of combustion at a ratelower than that in the normal combustion operation.

3. A liquid fuel burner as defined in claim 1, wherein said airflowpassage formed between the inner and outer casings is located adjacent acombustion region and a heater is provided around that portion of theouter peripheral surface of said inner casing which extends into saidairflow passage, said heater being energized only at the initiation ofcombustion.

4. A liquid fuel burner as defined in claim 3, wherein the airsuckingopening of said alrflow passage is shielded form the combustion regionby a shielding member and air is sucked into said airflow passage fromthe side remote from the combustion region with respect to saidshielding member.

5. A liquid fuel burner as defined in claim 1, wherein said atomizer isa cup-shaped depression formed at the center of an upper plate of saidSilocco fan and having a number of atomizing holes perforated in theperipheral wall thereof and said fuel supply means is a fuel supply pipeextending upwardly and exteriorly of said Silocco fan with the dischargeend thereof being spaced above the upper plate of said Silocco fan andextending downwardly toward said atomizer.

6. A liquid fuel burner as defined in claim 5, wherein fuelreceivingplates are mounted on the fuel supply pipe within the gasificationchamber for receiving the fuel flowing down on the outer wall of saidpipe.

7. A liquid fuel burner as defined in claim 1, wherein a mixing ring, acombustion ring and a headplate for closing the open top end of saidgasification chamber are provided on the open top edge of said innercasing one on another in the order mentioned with circumferentiallyspaced spacers interposed between each other, the resultant slit-shapedgaps being utilized as flame openings, and the inner edge of said mixingring is projected into the gasification chamber.

8. A liquid fuel burner as defined in claim 1, which further comprises afuel supply deice comprising a main tank provided with a level adjustingmechanism and having an inlet for fuel from a fuel tank, an auxiliarytank smaller in capacity than said main tank communicating with saidmain tank at a level above a set level of fuel in the main tank andhaving an outlet for fuel at a level lower than said communicatinglevel, and a pump for pumping the fuel from said main tank into saidauxiliary tank, the pump having a pumping capacity greater than the flowrate of fuel discharged through said outlet; and a fuel supply pipe forsupplying the fuel to said atomizer is communicated to said outletthrough a solenoid valve.

9. A liquid fuel burner comprising an inner casing defining agasification chamber therein and having an air passage hole formed inthe bottom wall thereof; said inner casing further having a mixing ringsmaller in inner diameter than said inner casing, a combustion ring anda closure headplate mounted on the open top edge thereof withcircumferentially spaced spacers interposed between each other so as toform slitshaped flame openings; an outer casing surrounding said innercasing; an airflow passage formed between said inner and outer casingswith a portion thereof located adjacent the flames formed at said flameopenings and with an air-sucking end thereof being covered by the flexededges of said inner and outer casings from above and the radiallyoutside thereof; a heater wound around the outer peripheral surface ofsaid inner casing within said airflow passage; a Silocco fan disposed inthe center of said gasification chamber to suck the air in said airflowpassage through said air passage hole in the bottom wall of said innercasing at the center thereof and disperse the same radially outwardly bythe blades thereof; an atomizer rotating integrally with said Siloccofan to disperse the liquid fuel supplied thereto radially outwardlyunder the influence of centrifugal force; a mounting frame providedbeneath said outer casing with a space therebetween; a motor mounted onsaid mounting frame with the drive shaft thereof extending upwardly andconnected directly to said Silocco fan; and a fan fixedly mounted on thedrive shaft of said motor for rotation therewith to cool said motor andform a layer of airflow in the space between said outer casing and saidmounting frame.

1. A liquid fuel burner comprising a burner casing consisting of aninner casing defining therein a gasification chamber communicating withflame holes and an outer casing surrounding said inner casing anddefining an airflow passage between it and said inner casing, a Siloccofan disposed in the central portion of said gasification chamber to suckthe air in said airflow passage at the center thereof and disperse thesame radially outwardly, a fuel atomizer provided in the central portionof said Silocco fan for rotation therewith and adapted to atomize theliquid fuel under the influence of centrifugal force, means forpreheating the air passing through said air flow passage and saidgasification chamber, and means for supplying the fuel to said atomizer.2. A liquid fuel burner as defined in claim 1, wherein means is providedto rotate said Silocco fan at the initiation of combustion at a ratelower than that in the normal combustion operation.
 3. A liquid fuelburner as defined in claim 1, wherein said airflow passage formedbetween the inner and outer casings is located adjacent a combustionregion and a heater is provided around that portion of the outerperipheral surface of said inner casing which extends into said airflowpassage, said heater being energized only at the initiation ofcombustion.
 4. A liquid fuel burner as defined in claim 3, wherein theair-sucking opening of said aIrflow passage is shielded from thecombustion region by a shielding member and air is sucked into saidairflow passage from the side remote from the combustion region withrespect to said shielding member.
 5. A liquid fuel burner as defined inclaim 1, wherein said atomizer is a cup-shaped depression formed at thecenter of an upper plate of said Silocco fan and having a number ofatomizing holes perforated in the peripheral wall thereof and said fuelsupply means is a fuel supply pipe extending upwardly and exteriorly ofsaid Silocco fan with the discharge end thereof being spaced above theupper plate of said Silocco fan and extending downwardly toward saidatomizer.
 6. A liquid fuel burner as defined in claim 5, whereinfuel-receiving plates are mounted on the fuel supply pipe within thegasification chamber for receiving the fuel flowing down on the outerwall of said pipe.
 7. A liquid fuel burner as defined in claim 1,wherein a mixing ring, a combustion ring and a headplate for closing theopen top end of said gasification chamber are provided on the open topedge of said inner casing one on another in the order mentioned withcircumferentially spaced spacers interposed between each other, theresultant slit-shaped gaps being utilized as flame openings, and theinner edge of said mixing ring is projected into the gasificationchamber.
 8. A liquid fuel burner as defined in claim 1, which furthercomprises a fuel supply device comprising a main tank provided with alevel adjusting mechanism and having an inlet for fuel from a fuel tank,an auxiliary tank smaller in capacity than said main tank communicatingwith said main tank at a level above a set level of fuel in the maintank and having an outlet for fuel at a level lower than saidcommunicating level, and a pump for pumping the fuel from said main tankinto said auxiliary tank, the pump having a pumping capacity greaterthan the flow rate of fuel discharged through said outlet; and a fuelsupply pipe for supplying the fuel to said atomizer is communicated tosaid outlet through a solenoid valve.
 9. A liquid fuel burner comprisingan inner casing defining a gasification chamber therein and having anair passage hole formed in the bottom wall thereof; said inner casingfurther having a mixing ring smaller in inner diameter than said innercasing, a combustion ring and a closure headplate mounted on the opentop edge thereof with circumferentially spaced spacers interposedbetween each other so as to form slit-shaped flame openings; an outercasing surrounding said inner casing; an airflow passage formed betweensaid inner and outer casings with a portion thereof located adjacent theflames formed at said flame openings and with an air-sucking end thereofbeing covered by the flexed edges of said inner and outer casings fromabove and the radially outside thereof; a heater wound around the outerperipheral surface of said inner casing within said airflow passage; aSilocco fan disposed in the center of said gasification chamber to suckthe air in said airflow passage through said air passage hole in thebottom wall of said inner casing at the center thereof and disperse thesame radially outwardly by the blades thereof; an atomizer rotatingintegrally with said Silocco fan to disperse the liquid fuel suppliedthereto radially outwardly under the influence of centrifugal force; amounting frame provided beneath said outer casing with a spacetherebetween; a motor mounted on said mounting frame with the driveshaft thereof extending upwardly and connected directly to said Siloccofan; and a fan fixedly mounted on the drive shaft of said motor forrotation therewith to cool said motor and form a layer of airflow in thespace between said outer casing and said mounting frame.